Maximum Opening Position Research Articles

Length of the occlusal glide at the lower incisal point during chewing

The purpose of this study was to estimate the length of the occlusal glide during gum chewing at the lower incisal point. Mandibular excursions with occlusal contacts in 25 females with permanent dentition were recorded using an optoelectronic system that can measure mandibular movement with 6 d.f. at a sampling frequency of 100 Hz. A curved mesh diagram of incisor coordinates during maximum mandibular excursions (CMDME) was plotted. Gum chewing movement was also measured using the same system and computer software which divided the chewing movement into cycles at each maximum opening position. Each cycle was standardized at 0.1 mm intervals from the most closed position. Finally, the distance between the CMDME and each position of the incisor during a chewing cycle was calculated. Whenever, this distance was less than 0.2 mm opposing teeth were considered to be in contact. The occlusal glide was defined as the distance travelled by the lower incisal point as the mandible moved along occlusal contacts of the CMDME. The vertical coordinates at the beginning of the occlusal glide (during closing) and at the end of occlusal glide (during opening) were also calculated. The lengths of the occlusal glide pathway averaged 1.29 mm during closing and 1.55 mm during opening, a total length of 2.84 mm. Mean vertical coordinates at the beginning and end of the glide were -0.95 and -1.12 mm from intercuspal position, respectively.

In vitro pulsatile flow visualization on extracardiac conduits for the right ventricular outflow tract reconstruction: qualitative considerations.

Valved homograft conduits play an important role in the right ventricular outflow tract (RVOT) reconstruction for the surgical treatment of complex congenital heart disease. An excellent immediate rather than long-term outcome could be obtained. The hemodynamics for late failure, however, remained unclear. In vitro pulsatile flow visualization was not conducted before. A simplified right heart duplicator system was set up and driven under physiologic conditions. Polystyrene of 0.18 mm in diameter was applied as the tracing particle. Flow characteristics of models of normal pulmonary circulation as well as pulmonary artery atresia with the RVOT reconstructed utilizing valved and non-valved extracardiac conduits were observed. Flow patterns in the normal pulmonary circulatory model were mainly of axial flow associated with small scope of flow disturbances. A single vortex in the right ventricle was noted in diastole. In the pulmonary artery atresia model, a couple of vortexes were found in the right ventricle, a secondary flow in the main pulmonary artery, and a stronger secondary flow than in the normal pulmonary circulatory model in the two branches in both systole and diastole. A secondary flow was found in the proximal, an axial flow was observed in the distal portion of the extracardiac conduit with normal bioprosthetic valves and a secondary flow was observed in the entire conduit with stenotic bioprosthetic valves. The secondary flow intensity became stronger with the development of the stenosis. Severe insufficiency occurred in the bileaflet ceramic tilting-disc prosthesis during the entire cardiac circle, i.e., the prosthesis was in a maximum open position. Severe reverse flow could be found in the extracardiac conduit in the deceleration phase. Concavity of the crank shaft was found by examination to be filled with tracing particles and the prosthesis became stuck. Model of RVOT reconstruction with non-valved conduit yielded reverse flow inside the extracardiac conduit as well. Secondary flow may occur in normal or diseased extracardiac conduit for RVOT reconstruction. If micro-thrombus of over 0.18 mm in diameter attached in the concave of the crank shaft of a bileaflet tilting-disc prosthesis under a condition of resistance as occurred in the present study, the prosthesis may become stuck. Model of RVOT reconstruction with non-valved extracardiac conduit yielded reverse flow inside the conduit, of which the flow pattern was of greater energy consumption. Thus, a non-valved conduit should be avoided in clinical practice as far as possible.

有歯顎者におけるそしゃく時口唇の動き

Lips and cheeks play an important role in masticatory functions. The purpose of this study was to analyze the lip movements of the dentulous subjects with the mandibular movements during mastication using 3-D Auto Tracking System. The subjects were 28 males and 22 females, and 8 types of test-foods (chewing gum, caramel, gummy-jelly, peanuts, cookie, carrot, two sizes of boiled fish paste) were used. The measuring point of the lips was placed on the mouth corner and that of mandibular movements was placed on the surface of the chin.The length of the trace on each chewing cycle was evaluated as the index of the lip's activity. One sequence of mastication was divided into three (first, middle and last) stages. Time dependent changes of the lip's activity were evaluated statistically.The results were as follows:1. During tapping, the mouth corner moved to-and-fro between the rest position and the maximum opening position.2. On the chewing side, the mouth corner was tear drop shaped, and on the non-chewing side, shuttled simply.3. The lip's activity during mastication depended on the physical property of the test food.4. As the mastication proceeded, the ratio of the lip's activity to the mandibular movements increased in all test foods except for gum.

相互相関法からみた骨格性下顎前突症患者のそしゃく筋筋活動パターン

The purpose of this study was to investigate EMG profiles of masticatory muscles in orthognathic surgery patients with mandibular prognathism during deliberate unilateral gum chewing.Vertical jaw movement and EMG activities from bilateral anterior temporal, masseter, and anterior belly of digastric muscles were recorded simultaneously from 12 healthy adults and 12 patients. EMG signal was divided according to the period of the maximum opening position of vertical jaw movement. EMG profiles of the chewing stroke were accomplished by normalizing each period to 100%. Normalization was achieved by setting the mean value of each EMG over the chewing cycle to 100%. The relationship of the EMG profile between normal subjects and patients was evaluated. The degree of similarity and the displacement for each EMG profile in all muscles was investigate by using a cross-correlation technique.The results were as follows:1. EMG profiles of patients were different for the “Peak” vale and “Duration” of the activity from those of normal subjects.2. The similarity was little, and great displacement was found in patients.3. In patients, the similarity and displacement of EMG profiles had large value on the working side.

食品テクスチャーの違いがそしゃく筋筋活動パターンに与える影響

A study was conducted for the purpose of grasping the influence of food characteristics on electromyographic (EMG) patterns during mastication. Cheese, kamaboko, takuan, senbei, surume and gumi were used as test food. Vertical jaw movement and EMG activities were recorded simultaneously from 10 healthy adults. EMG signal was divided according to the period of the maximum opening position of vertical jaw movement.EMG profile for chewing stroke was accomplished by normalizing each period to 100% from the beginning of mastication to swallowing. The relationship between the texture of test materials and the EMG profiles was evaluated.The obtained results were as follows:1. The EMG profile of each test material showed various patterns. The degree of variability in the masseter was larger than that in the temporal and digastric muscles.2. Owing to the delay of the onset of EMG activity, the duration of activity in the temporal and masseter muscle was shortened as mastication progressed.3. Cheese showed the largest difference between the beginning of mastication and just before swallowing in the EMG profile of the temporal and masseter muscles. Surume showed least change in the EMG profile.

Transducing Jaw and Lip Movements in Speech

Various schemes for easily and accurately transducing lip and jaw movements into an analog voltage have been explored. Considerations of cost, simplicity, linearity, and the need to maintain natural articulation in speech led to the development and construction of a device involving a simple optical system and a photocell. The device can track in any dimension the position of one or more tiny lights attached to the lips and/or jaw. Using the device a few simple experiments were conducted involving jaw deflection, velocity and acceleration. The experimental finding of Kozhevnikov et al. (Speech: Articulation and Perception, 1965) that the peak velocity of the lower lip on closing for a consonant varies proportionately with its maximum open position was found to be true of the jaw, too. [This research was partially supported by the National Institutes of Health, U. S. Department of Health, Education and Welfare, and the Office of Naval Research.]